Delaying arm fuze principle

ABSTRACT

A delay arming fuze for a fin stabilized mortar round or rocket for the prevention of premature arming of the fuze while the round is in the mortar tube. The fuze consists of a fuze head which has axial bores, a spring biased striker carrying a firing pin slidable in the bores, a radially slotted adapter carried by the striker and a plurality of steel balls which, when the round is in a mortar tube assume a position rearward of the adapter to maintain the fuze unarmed. When the round is fired acceleration forces hold the balls in their rearward position until the round decelerates, at which time the balls under inertial forces roll forward through the radial slots in a metered manner to the forward side of the adapter to arm the fuze and to thereby permit firing upon target impact. The metering effect is produced by providing more balls than there are radial slots in the adapter so that all of the balls cannot enter the slots at the same moment. Relative movement between the round and the balls which are subjected to the same gravitational forces is due to the fact that the round is subjected to frictional resistance of the atmosphere through which it passes and therefore decelerates more rapidly than the balls which are not subjected to such resistance.

Hittite States atent [191 Bruno [4 1 Jan. 1,1974

[ DELAYING ARM FUZE PRINCIPLE [76] Inventor: Onofrio P. Bruno, 237Rogers St.,

Aberdeen, Md. 21005 [22] Filed: Dec. 15, 1971 [21] Appl. No.: 208,061

521 U.s. Cl. 102/76 R, 102/78 Primary Examiner-Samuel W. EngleAttorney-Harry M. Saragovitz et al.

[5 7] ABSTRACT A delay arming fuze for a fin stabilized mortar round orrocket for the prevention of premature arming of the fuze while theround is in the mortar tube. The fuze consists of a fuze head which hasaxial bores, a spring biased striker carrying a firing pin slidable inthe bores, a radially slotted adapter carried by the striker and aplurality of steel balls which, when the round is in a mortar tubeassume a position rearward of the adapter to maintain the fuze unarmed.When the round is fired acceleration forces hold the balls in theirrearward position until the round decelerates, at which time the ballsunder inertial forces roll forward through the radial slots in a meteredmanner to the forward side of the adapter to arm the fuze and to therebypermit firing upon target impact. The metering effect is produced byproviding more balls than there are radial slots in the adapter so thatall of the balls cannot enter the slots at the same moment. Relativemovement between the round and the balls which are subjected to the samegravitational forces is due to the fact that the round is subjected tofrictional resistance of the atmosphere through which it passes andtherefore decelerates more rapidly than the balls which are notsubjected to such resistance.

2 Claims, 2 Drawing Figures DELAYING ARM FUZE PRINCIPLE The inventiondescribed herein may be manufactured, used and licensed by or for theGovernment of the United States for governmental purposes withoutpayment to me of any royalty thereon.

SUMMARY Premature functioning of the fuze of a fin stabilized mortarround or rocket has occurred while the round is in the firing tube of amortar or rocket launcher or in close proximity thereof, due tomalfunctioning of the fuze, mishandling or by the round coming incontact with nearby foliage, etc. This premature arming has resulted ininjury and even death to many personnel.

The present invention provides a fail-safe, delayed arming fuze toeliminate the aforesaid dangers by a delayed arming means consisting ofa plurality of steel balls that prevents inward movement of a firing pinwhile the round is dropping in a mortar tube or being accelerated out ofthe tube. Upon deceleration the steel balls roll forward throughmetering slots in an adapter carried by the striker and pin assembly tothe forward side thereof and permit the firing pin to function upontarget impact. It is therefore a primary object of this invention toprevent premature arming of the fuze in a mortar tube or its immediateenvirons.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial section takenthrough the fuze of this invention, and,

FIG. 2 is a perspective view of the adapter.

Referring in detail to the drawing wherein, in FIG. 1, referencecharacter 1 indicates generally, the fuze of this invention. A fuze head2 is provided with a large outer bore 3, a lower bore 4 of less diameterthan bore 3 and an intermediate bore 5. A striker, generally indicatedby 6, is slidably mounted in bore 3 and consists of a cap 7. A firingpin 8 is secured centrally to cap 7 by suitable means such as a rivet 9,etc. Firing pin 8 extends inwardly through bores and 4 and terminates ina point 10. Cap 7 is biased outward by a coil spring 11 which encirclesfiring pin 8 and its outward movement is limited by a locking ring 12fixed to its lower portion and in bore 4. A shoulder formed by bores 4and 5 is extended into an inwardly projecting annular flange 26 at thelower end of bore 5 and retains firing pin 8 against the aforesaidoutward movement, as shown. An adapter, generally indicated by 13 iscarried by cap 7. Adapter 13 consists of a cylindrical block 14 having aflange 15. Block 14 fits into the skirt of cap 7 by press fitting orsimilar methods. Flange 15 butts against the rim of the skirt so thatthere is a space .16 between the outer end of adapter 13 and the end ofcap 7. Block 14 is provided with a central bore 17 which receives atubular liner 18 which has a restricted portion 19 at its outer end toprovide a retaining means for spring 11 which will bias in the usualmanner between bore flange 26 and restricted portion 19. Liner 18 isretained in bore 17 by a sleeve 20. Block 14 is provided with radialbores 21, see FIG. 2. There are four radial bores shown in FIG. 2 buttheir number can be varied as desired. Anning means is provided for fuzel and consists of a plurality of steel balls 22 which are shown in FIG.l to be disposed on the inward side of adapter 13 which is the positionto unarm the fuze. For additional safety, if desired, a safety pin 23could be placed in a transverse bore in head 2 so that it would bedisposed adjacent the inner side of locking ring 12, the pin 23 to beremoved prior to dropping the round in the mortar tube for firing. Theballs each have a diameter less than the width or effective diameter ofeach slot but substantially greater than half such width or effectivediameter of the slot so that no two balls can pass through a single slotabreast.

In operation, the fuze 1 will be mounted in the usual manner to a mortarround, not shown, by threads 25 on head 2. The round with fuze 1 is heldin an upright manner so that balls 22 will roll, if in space 16, throughslots 21 and into space 24 where they will be in a position to preventinward movement of striker 6 and adapter 13 to accidentally fire theround. Balls 22 will remain in this position while the round is firedand during its acceleration in trajectory, so that should cap 7 come incontact with foliage, etc. in proximity to the mortar, the round cannotbe exploded. When balls 22 roll through slots 21 to space 16 they willbe out of action and will permit striker 6, adapter 13 and firing pin 8to move inward upon target impact to fire the round.

The number of slots 21 and the greater number of balls 22 will be suchthat a metered effect is obtained to provide arming delay to the fuzefunctioning.

The principle of operation of this device involves the introduction of adelay in arming due to the movement of the balls through the radialbores, from the unarmed to the armed position, where the movement is dueto the differences in deceleration forces acting on the balls and otherfuze components during the flight trajectory of the round. The need forsuch arming mechanism is great in applications where there isinsufficient spinning of the round to actuate centrifugal armingmechanisms.

It is apparent that a simple yet highly efficient delay mechanism for afuze has been devised by the present invention.

What is claimed is:

1. A delayed arming mechanism for a fin stabilized round fuze includinga head having a series of axially aligned bores therethrough, comprisinga detonating striker slidably mounted in the outermost bore of the head,a block carried by the striker for movement therewith within suchoutermost bore, resilient means within the head to bias the striker andblock in a forward direction, to provide a chamber in one of the boresbehind the block to receive the balls, there being a series ofindependent slots extending longitudinally completely through saidblock, and a plurality of balls of greater number than there are slotsin the block, said balls each having a diameter less than the effectivediameter of each slot, but substantially greater than half sucheffective diameter of the slot so that they will roll through the slotsin a metered manner whereby when said fuze is in an upright positionsaid balls will roll through said slots to an operative position inwardof the block to prevent inward movement of the detonating striker, andwhen said fuze is decelerated in flight the balls will roll through saidslots to an inoperative position forward of the block to thereby placethe fuze in an armed condition.

2. The device of claim l in which the block is of cylindricalconfiguration of a size to snugly fit within the outermost bore of thehead, a hollow cup carried by the outer end of the striker and engagingthe outer end of the block to form a chamber for reception of the ballswhich pass forwardly through the block during deceleration of the fuze,the forwardly biased striker normally diameter of each ball so as toprovide a chamber for the being held in a position in which the rearwardend of reception of the balls behind the block during the unthe block isspaced above the rearward end of the outarmed safety position of thefuze.

ermost bore a distance substantially greater than the

1. A delayed arming mechanism for a fin stabilized round fuze includinga head having a series of axially aligned bores therethrough, comprisinga detonating striker slidably mounted in the outermost bore of the head,a block carried by the striker for movement therewith within suchoutermost bore, resilient means within the head to bias the striker andblock in a forward direction, to provide a chamber in one of the boresbehind the block to receive the balls, there being a series ofindependent slots extending longitudinally completely through saidblock, and a plurality of balls of greater number than there are slotsin the block, said balls each having a diameter less than the effectivediameter of each slot, but substantially greater than half sucheffective diameter of the slot so that they will roll through the slotsin a metered manner whereby when said fuze is in an upright positionsaid balls will roll through said slots to an operative position inwardof the block to prevent inward movement of the detonating striker, andwhen said fuze is decelerated in flight the balls will roll through saidslots to an inoperative position forward of the block to thereby placethe fuze in an armed condition.
 2. The device of claim 1 in which theblock is of cylindrical configuration of a size to snugly fit within theoutermost bore of the head, a hollow cup carried by the outer end of thestriker and engaging the outer end of the block to form a chamber forreception of the balls which pass forwardly through the block duringdeceleration of the fuze, the forwardly biased striker normally beingheld in a position in which the rearward end of the block is spacedabove the rearward end of the outermost bore a distance substantiallygreater than the diameter of each ball so as to provide a chamber forthe reception of the balls behind the block during the unarmed safetyposition of the fuze.